Proliferation rate of colonic mucosa in normal subjects and patients with colonic neoplasms: a refined immunohistochemical method

Eicosapentaenoic acid (EPA) reduces crypt cell proliferation and increases apoptosis in normal colonic mucosa in subjects with a history of colorectal adenomas

BACKGROUND AND AIMS

Omega-3 fatty acids in fish oil exert a protective effect on the development of colorectal cancer in animal models. Patients with colorectal adenomas have been shown to have increased crypt cell proliferation and decreased apoptosis in macroscopically normal appearing colonic mucosa. We investigated whether dietary supplementation with eicosapentaenoic acid (EPA) could alter crypt cell proliferation and apoptosis in such patients.

PATIENTS/METHODS

Thirty subjects were randomised to either 3 months of highly purified EPA in free fatty acid form (2 g/day) or to no treatment. Colonic biopsies were taken at the initial colonoscopy and repeated 3 months later, and analysed for cell proliferation and apoptosis (immunohistochemistry) and mucosal fatty acid content.

RESULTS/FINDINGS

Crypt cell proliferation was significantly reduced whilst apoptosis was significantly increased after EPA supplementation. Neither crypt cell proliferation nor apoptosis were altered in the control group. EPA in the mucosa increased significantly after EPA supplementation, whereas there was no significant change in controls.

CONCLUSIONS

Dietary supplementation with EPA significantly increases levels of this fatty acid in colonic mucosa, associated with significantly reduced proliferation and increased mucosal apoptosis. Further studies are needed to assess the potential efficacy of EPA supplementation in preventing polyps in the chemoprevention of colorectal cancer.

Calcium or resistant starch does not affect colonic epithelial cell proliferation throughout the colon in adenoma patients: a randomized controlled trial

Patients with a history of sporadic adenomas have increased epithelial cell proliferative activity, an intermediate risk marker for colorectal cancer. Reduction of proliferation by dietary intervention may reflect a decreased colorectal cancer risk. To evaluate whether calcium or resistant starch could reduce proliferative activity throughout the colon, we performed a randomized controlled trial in 111 sporadic adenoma patients. Patients received two placebos, 1 g of calcium + placebo, or 30 g of amylomaize (19 g of resistant starch) + placebo. After 2 mo, biopsies were collected from the cecum, transverse and sigmoid colon, and rectum during colonoscopy. Epithelial cell proliferation was determined by dividing the number of 5-bromo-2-deoxyuridine-labeled nuclei by the total number of nuclei x 100 (labeling index, LI). LI of luminal, mid, and basal compartments was determined. Twenty-five patients dropped out. In the remaining 86 patients (28 treated with placebo, 30 with calcium + placebo, and 28 with resistant starch + placebo), no difference was observed in total LI, the LI of the three compartments, or the crypt length in the four areas of the colorectum. Colonic epithelial cell proliferative activity throughout the colon of sporadic adenoma patients is not affected by supplementation with 1 g of calcium or 19 g of resistant starch.

Effect of tumor removal on mucosal protein synthesis in patients with colorectal cancer

It is currently controversial whether mucosal hyperproliferation is involved in colorectal cancerogenesis. The purpose of the present study was to examine protein synthetic rate as an indicator of potential tissue proliferation in grossly normal rectal mucosa from cancer-bearing subjects and to compare this rate with that in mucosa from subjects posttumor removal. Six postabsorptive patients with localized rectal cancer and five postsurgical control subjects received a primed constant infusion of [1-(13)C]leucine (0.16 micromol/kg min, 9.6 micromol/kg prime). Forceps biopsies from the mucosa were taken after 3 and 6 h. Protein synthesis was calculated from protein-bound leucine enrichment (determined by capillary GC-combustion IRMS) and from the enrichment of free intracellular leucine (determined by GC-quadrupole MS). In cancer-bearing subjects, mucosal protein synthesis amounted to 1.28 +/- 0.24%/h. This rate was significantly higher (P < 0.05) than the corresponding rate of mucosa from patients after cancer removal (0.69 +/- 0.09%/h). These findings do not support the concept that colorectal cancer originates from a proliferative disease of the whole colon. Increased mucosal protein synthesis appears to depend on the presence of the tumor itself and should therefore be considered a secondary phenomenon.

Calcium affects biomarkers of colon carcinogenesis after right hemicolectomy

BACKGROUND

In Western societies colonic cancer most frequently develops in the distal colon, largely as a result of the composition of the diet. Modulation of dietary factors is therefore an attractive modality to reduce colorectal cancer risk. This study aims to evaluate the potentially protective effects of calcium in right hemicolectomy patients.

MATERIALS AND METHODS

A randomized controlled cross-over intervention trial was performed with 1000 mg of elemental calcium per day for 2 months in 15 right hemicolectomy patients. Primary endpoints were proliferative activity, determined by immunohistochemical detection of BrdU-labeled cells (LI) in rectal biopsies, and cytotoxicity and alkaline phosphatase activity of faecal water. Secondary endpoints were bile acid composition in faeces.

RESULTS

Calcium-reduced LI in the superficial one-third of the crypt (from 0.84 +/- 0.27% to 0.37 +/- 0.08%, P = 0.04) and a trend towards a lower total LI and LI in the mid one-third of the crypt was observed. Alkaline phosphatase activity was reduced from 6.2 +/- 2.6 U mL-1 in the placebo period to 4.6 +/- 2.2 in the calcium period (P = 0.02), and a trend toward a lower cytotoxicity of faecal water was observed. No effect on total bile acids in faeces was observed, but calcium increased the percentage of deoxycholic acid (from 49.6 +/- 7.0% to 56.5 +/- 6.2%, P = 0.03) and decreased the percentages of cholic acid (from 10.3 +/- 4.7% to 5.8 +/- 2.7%, P = 0.05) and lithocholic acid (from 26.7 +/- 3.4% to 23.9 +/- 2.9%, P = 0.04).

CONCLUSION

Calcium may have a protective effect against colorectal cancer risk in right hemicolectomy patients.

Early cellular events in colorectal carcinogenesis

Colorectal cancer develops through a multistage process recognizable at a histopathological level by progression from normal mucosa to invasive carcinoma (the adenoma-carcinoma sequence). For many years, it has been hypothesized that increased cell proliferation in the colonic crypt represents the earliest recognizable stage in this sequence. This perspective is now changing. While several human studies have reported increased crypt cell proliferation in samples from at-risk patients, there are many inconsistencies and paradoxes in their conclusions. In addition, it is appreciated that the process of apoptosis (programmed cell death) is vital for normal crypt homeostasis and its impairment may be an early event in the neoplastic process. It is now believed that aberrant crypt foci (ACFs) represent the earliest step in colorectal carcinogenesis. Two ACF types are identifiable: hypercellular and dysplastic. Increased proliferative activity may be seen in both, but the dysplastic entity is most relevant to carcinogenesis. Animal and human studies support the notion that ACFs grow by crypt fission leading to the formation of microadenomas. Adenomas are monoclonal expansions of an altered cell, but very early lesions may be polyclonal. There are outward and inward theories of polypoid growth, and evidence to support both mechanisms. The ACF assay has become a useful tool to detect carcinogens in animal studies but has been less frequently used in human studies. For future cancer chemopreventive and risk assessment studies in humans, the identification and quantification of ACFs should be considered a more effective intermediate marker of risk than the determination of crypt cell proliferation alone.

In vitro labelling studies and the measurement of epithelial cell proliferative activity in the human oral cavity

Samples (110) of human mandibular gingiva and buccal mucosa, harvested from patients undergoing third-molar surgery, were subjected to in vitro labelling with tritiated thymidine, bromodeoxyuridine, or a sequential double-labelling technique comprising tritiated thymidine followed by bromodeoxyuridine, in order to determine the efficacy of a new incubation labelling technique, and to characterize S-phase labelling indices in human oral mucosa. Whilst, there were no demonstrable differences in labelling indices obtained by single thymidine, single bromodeoxyuridine or double labelling, there was a significant difference between anatomical sites, with higher S phase labelling observed in buccal mucosa (mean LI 11.7) than mandibular gingiva (mean LI 8.5; P<0.01). There was, however, no significant correlation between individual labelling indices and patient age, sex or the time of day when tissue was harvested. The in vitro labelling technique provides a reliable and quantifiable method of characterizing proliferative labelling indices in the human oral cavity. Further investigation is being carried out to profile wider age and anatomical ranges and to utilize the double-labelling technique to calculate S-phase durations and cell-cycle times. These profiles may have a future role in the assessment of oral mucous membrane disease.

Effect of elimination of acid reflux on epithelial cell proliferative activity of Barrett esophagus

BACKGROUND

Barrett esophagus (BE) is a premalignant condition resulting from chronic acid gastroesophageal reflux and is associated with increased epithelial cell proliferation. Elimination of acid reflux might decrease cancer risk by affecting cell proliferation in BE. The effect of elimination of acid reflux on epithelial cell proliferation in BE was studied.

METHODS

Forty-five patients with long segment Barrett esophagus were treated in a randomized 2-year follow-up study with either omeprazole 40 mg b.i.d. (OME) or ranitidine 150 mg b.i.d. (RAN) and were compared for the effect on epithelial cell proliferation. Biopsies were taken 3 cm above the GE junction and just below the Z-line, at 0, 3, 9, and 24 months. Epithelial cell proliferation was determined by in vitro labeling with 5-bromo-2-deoxyuridine and immunohistochemistry. Labeling indices (LI) were established for luminal and crypt epithelium separately. Ambulatory 24-h esophageal pH-metry was performed at 0 and 3 months. Comparisons were made for the timeframes 0-3 months, 3-24 months, and 0-24 months.

RESULTS

OME reduced mean acid reflux to 0.1 %/24 h, RAN to 9.4%. In the distal and the proximal biopsies, change in LI after 3 months was n.s. at either level for both treatments. In the distal biopsies (OME 22, RAN 23 patients) luminal LI increased significantly for RAN from 3 to 24 months (+12.64% month, mean area under the curve (AUC)), while that for OME remained stable, RAN versus OME P < 0.05. Crypt LI increased in both groups, only in RAN significantly so (+30.75% month), RAN versus OME n.s. In the proximal biopsies luminal LI at 24 months (OME 20, RAN 21 patients) had increased slightly but not significantly in RAN (+8.86% month), RAN versus OME n.s., whereas in the crypts LI in OME it had increased significantly (+28.80% month), OME versus RAN n.s.

CONCLUSION

Elimination of acid reflux resulted in a stabilization of luminal cell proliferative activity of Barrett epithelium in the distal esophagus, whereas this activity increased during continued acid reflux. Whether this finding has any implication for the cancer risk in Barrett esophagus remains to be seen.

One year growth hormone replacement therapy does not alter colonic epithelial cell proliferation in growth hormone deficient adults

OBJECTIVE

Increased colonic epithelial cell proliferation has been found in various conditions associated with increased risk of colorectal cancer including acromegaly. In a placebo-controlled study we determined the effect of growth hormone (GH) replacement therapy in GH deficient adults on the colonic epithelial proliferation rate.

PATIENTS AND DESIGN

Sixteen GH deficient adults were randomised to low dose GH therapy (1 U (0.5 mg) subcutaneously per day, n = 5), high dose GH therapy (2 U daily, n = 5) or placebo (n = 6) during 6 months. Thereafter, all patients were treated with 2 U of GH daily during a 6-months open extension period.

MEASUREMENTS

Plasma Insulin-like growth hormone I (IGF-I) and IGF binding protein 3 (IGF BP3) concentrations were measured using commercial RIA kits. The colonic epithelial proliferation rate, expressed as overall crypt labelling index (LI) using 5-bromo-2'-deoxyuridine (BrdU) immunostaining, was determined at baseline, after 6 months treatment and at the end of the 6 months open extension period.

RESULTS

IGF-I rose from 8.9 +/- 6.7 to 34.6 +/- 20.0 nmol/l after 6 months in 8 GH treated patients (P < 0.01 from baseline; P < 0.01 from change with placebo). In the extension study, plasma IGF-I was also increased in the patients who previously received placebo (P < 0.02, n = 5). LI was evaluable in 14 biopsies at baseline, in 16 after 6 months and in 14 after 12 months. Overall crypt LI did not change in 8 GH treated patients after 6 months (P > 0.40 from baseline; P > 0.80 from change with placebo). In the extension study, overall crypt LI was also unchanged in those patients who received GH after placebo (n = 5, P > 0.40) and in those who continued GH replacement (n = 9, P > 0.60; P > 0.80 from change in initially placebo treated patients). Separate evaluation of the LI at the basal, mid and luminal portions of the colonic crypts also did not reveal any effect of GH treatment on BrdU labelling.

CONCLUSIONS

Six to 12 months of GH replacement therapy, aimed to increase plasma IGF-I into the (high) physiological range, does not adversely affect colonic epithelial cell proliferation as a biomarker for the risk of development of colorectal cancer.

Predisposition to colonic dysplasia is unaffected by continuous administration of insulin-like growth factor-I for twenty weeks in a rat model of chronic inflammatory bowel disease

BACKGROUND

Insulin-like growth factor-I (IGF-I) is currently under evaluation for the treatment of a variety of chronic disease conditions. We investigated the safety of long-term IGF-I administration in a rat model of inflammatory bowel disease which predisposes to the development of dysplasia.

METHODS

Chronic consumption of dextran sulphate sodium (DSS) by rats manifests a colitis with dysplastic features. Rats consumed 2% DSS for 4 weeks when pumps were implanted to deliver either vehicle or IGF-I for 15 or 20 weeks while rats continued to consume DSS. Features of colitis and dysplasia were assessed at kill.

RESULTS

Compared to vehicle, 20 weeks IGF-I significantly increased body weight by 19% and total gut weight by 43%. Colonic crypt depth, proliferative compartment, labelling index, dysplasia, neoplasia and other indices of colitis were not significantly affected.

CONCLUSIONS

Twenty weeks administration of IGF-I to rats induced growth of the intestine but did not affect the severity of experimentally-induced colitis or the incidence or progression of colonic dysplasia.

Epithelial cell proliferative activity of Barrett's esophagus: methodology and correlation with traditional cancer risk markers

Barrett's esophagus (BE) is a premalignant condition, due to chronic gastroesophageal reflux. Effective antireflux therapy may diminish cancer risk. To evaluate this option an intermediate marker is needed. We developed a methodology for measurement of epithelial cell proliferative activity of Barrett's mucosa as an intermediate marker and correlated the activity with traditional cancer risk markers and other parameters. Fifty-six patients (21-74 years of age) with Barrett's esophagus and established acid gastroesophageal reflux were included. Biopsies were taken from Barrett's mucosa at 3-cm intervals. Reflux was measured by 24-hr pH-metry. Proliferative activity was determined using in vitro labeling with 5-bromodeoxyuridine and immunohistochemistry and was expressed as labeling index (LI). The length of BE correlated with erect acid reflux (P=0.002). LI in specialized columnar metaplasia was higher than in gastric metaplasia, especially in crypt epithelium (P < 0.05). Multiple regression analysis revealed independent positive correlations for surface LI with dysplasia (P=0.011), distance from the incisors (P=0.041), and crypt LI (P=0.000). Crypt LI showed an independent positive correlation with the length of BE (P=0.033) and type of metaplasia (P=0.007). In conclusion, epithelial cell proliferative activity of BE correlates with several known risk factors for cancer. Proliferative activity is an attractive intermediate marker to evaluate the effects of interventional measures to decrease cancer risk in Barrett's esophagus.

Butyrate inhibits deoxycholate-induced increase in colonic mucosal DNA and protein synthesis in vivo

PURPOSE

Crypt surface hyperproliferation is an intermediate biomarker of colon cancer risk. In vitro studies indicate that the short-chain fatty acid and antineoplastic agent butyrate may reverse the crypt surface hyperproliferation induced by the secondary bile acid and tumor promoter, deoxycholate. We hypothesized that butyrate may reverse deoxycholate-induced crypt surface proliferation in vivo.

METHODS

Thirty-one Sprague-Dawley rats (250-300 g) underwent surgical isolation of the colon and 24-hour luminal instillation of either sodium chloride, butyrate, deoxycholate, or butyrate plus deoxycholate (all solutions, 2 ml; pH 7; total sodium = 20 mM). Study variables included colon weight, mucosal DNA, mucosal protein, and proliferating cell nuclear antigen immunohistochemistry, labeling of which was determined in five crypt compartments from base to surface (12 crypts per rat). Labeling indexes were calculated as proliferating cell nuclear antigen immunohistochemistry-labeled cells divided by total counted cells in the whole colonic crypt and each of five crypt compartments. The phi(h) value (an index of premalignant risk) was calculated as the ratio of labeled cells in the two surface compartments divided by the total labeled cells.

RESULTS

Deoxycholate significantly increased colon wet weight, mucosal protein, total crypt labeling indexes, crypt surface labeling indexes, and the phi(h) value and raised the mucosal DNA content. Butyrate alone slightly reduced total mucosal DNA and protein content. The combination of butyrate plus deoxycholate significantly decreased mucosal DNA and tended to reduce mucosal protein compared with deoxycholate alone. In contrast to prior in vitro findings, butyrate plus deoxycholate did not reverse the deoxycholate-induced surface hyperproliferative changes as measured by proliferating cell nuclear antigen labeling.

CONCLUSIONS

Because co-treatment with butyrate plus deoxycholate inhibits deoxycholate-induced increases in total mucosal DNA and protein content, we conclude that butyrate may play a role in maintaining the proliferative balance of the colonic mucosa, in vivo. However, co-treatment with butyrate plus deoxycholate does not reverse the deoxycholate-induced increases in colon weight and proliferating cell nuclear antigen labeling indexes under the studied experimental conditions.

Regional proliferative patterns in the colon of patients at risk for hereditary nonpolyposis colorectal cancer

Patients from a hereditary nonpolyposis colorectal cancer (HNPCC) kindred (Lynch Type 1 and Type 2) have an increased risk of developing large-bowel cancer. Tumors occur at a young age and are characteristically right-sided. Colonic mucosal proliferation is known to be increased in several groups of patients at risk of colorectal cancer.

PURPOSE

This study was performed to assess the pattern of mucosal proliferation at different sites in the colon of patients at risk of HNPCC and to determine whether this pattern differs from normal patients.

METHODS

Mucosal biopsies were obtained at colonoscopy from 21 patients at risk for HNPCC (16 females; mean age, 42 years) and from 7 normal patients (4 females; mean age, 38 years), and mucosal proliferation was quantified using the whole crypt mitotic count (WCMC) technique.

RESULTS

In patients from HNPCC families, WCMC and crypt area were significantly greater in the cecum than in the transverse colon and left colon (P < 0.001). Compared with normal patients, WCMC in HNPCC patients was significantly greater in the cecum only (P < 0.05). A significant right-to-left shift was also observed in normal patients, but the percentage increase from right to left was two-fold greater in HNPCC patients.

CONCLUSIONS

These results confirm a proximal-to-distal proliferative gradient in the human colon and suggest that this may be exaggerated in HNPCC. This increased proximal proliferative rate may be a factor in the development of right-sided cancer in these patients.

Growth kinetics of colorectal adenoma-carcinoma sequence: an immunohistochemical study of proliferating cell nuclear antigen expression

Tumorigenesis is a multistep process that begins with the abrogation of normal controls of cell proliferation. The authors examined the in vitro growth kinetics and compartment shift through the adenoma-carcinoma sequence of the human colon by determining the labelling indexes of proliferating cell nuclear antigen (PCNA) in normal mucosae (n = 10), adenomas (n = 88), and carcinomas (n = 20). Carcinoma cells had a significantly higher PCNA index than adenomas or control specimens (P = .0001). There also was a difference in the PCNA index between the histological subtypes of adenomas (P = .03), whereas no significant difference was observed for dysplastic grade, tumor size, or location (P > .1). Tubular and tubulovillous adenomas, adenomas with mild dysplasia, small (< 10 mm) adenomas, and proximally located adenomas revealed shift of cell proliferation toward the middle portion of the colonic glands. The PCNA in the villous, moderate or severe dysplastic, larger or distally located adenomas appeared to be diffuse (P = .04, 0.02, 0.07, and 0.06, respectively). In addition, the transitional mucosa neighboring carcinoma showed an elevation of the mean PCNA index together with an upward shift of cell proliferation compared with the controls (P = .03). These results suggest a stepwise increment of proliferating activity with compartment shift of the proliferating zone through the adenoma-carcinoma sequence. The information essentially supports contemporary understanding of the carcinogenic processes in the human colon.

Bromodeoxyuridine: a diagnostic tool in biology and medicine, Part III. Proliferation in normal, injured and diseased tissue, growth factors, differentiation, DNA replication sites and in situ hybridization

This paper is a continuation of parts I (history, methods and cell kinetics) and II (clinical applications and carcinogenesis) published previously (Dolbeare, 1995 Histochem. J. 27, 339, 923). Incorporation of bromodeoxyuridine (BrdUrd) into DNA is used to measure proliferation in normal, diseased and injured tissue and to follow the effect of growth factors. Immunochemical detection of BrdUrd can be used to determine proliferative characteristics of differentiating tissues and to obtain birth dates for actual differentiation events. Studies are also described in which BrdUrd is used to follow the order of DNA replication in specific chromosomes, DNA replication sites in the nucleus and to monitor DNA repair. BrdUrd incorporation has been used as a tool for in situ hybridization experiments.

Antiproliferative effects of the enantiomers of flurbiprofen

Nonsteroidal antiinflammatory drugs (NSAIDs) are recognized for inhibiting growth of colon tumors in animal models, and for reducing the risk of colon cancer in humans. The mechanisms involved have not been established, but are thought to be related to reduced prostaglandin biosynthesis. The present study investigates the effect of COX-inhibiting and non-COX-inhibiting enantiomers of flurbiprofen on rat colonocyte proliferation. Intestinal ulceration was used as a surrogate indicator of COX inhibition. Sprague Dawley rats were treated orally with 6.3 mg/kg of R- or s-flurbiprofen or vehicle. Colonocyte labeling index and small bowel ulcer index were measured. R-flurbiprofen and S-flurbiprofen significantly reduced colonocyte labeling index, by 34% and 23% respectively, compared with vehicle. R-flurbiprofen caused minimal ulcer formation (4.48 mm2) compared with S-flurbiprofen (94.4 mm2). These findings suggest that R-flurbiprofen-mediated control of colonocyte proliferation is independent of prostaglandin biosynthesis.

Bromodeoxyuridine: a diagnostic tool in biology and medicine, Part II: Oncology, chemotherapy and carcinogenesis

This paper follows on from Part 1 of my review of bromodeoxyuridine published earlier this year (Dolbeare, 1995).

Variability of neoplastic parameters in colon tumours, and its significance in diagnostic practice

We have reviewed the value of individual variability in the reaction of tissues to treatment with carcinogens, and the manifestation of this variability in different morphological (histological, morphometric, and ultrastructural), histochemical and immunohistochemical parameters generated in tumorous tissues. Moreover, we also reviewed data in the literature on individual variability in the manifestation of some biochemical and immunochemical markers which are accumulated in the serum of tumour-bearing patients and which are characteristic for the different phases of tumourigenesis. The high variability of different tumorous parameters suggests that none can be utilized alone as a conclusive marker of neoplasia and that only their combined use can give objective information. We also reviewed the impact of this variability in the evaluation of various pathological methods to detect different stages of neoplastic transformation in the colon. It has been concluded that none of the present approaches can be absolutely conclusive and without false results, and that objective information regarding early cancerous changes may be obtained only by use of combined analyses utilizing several laboratory methods. The diagnostic procedures should be based on the complex utilization of all appropriate methods using the quantitative interpretation of the obtained data. Multivariate analysis of many parameters should be very effective for the prediction of therapeutic results.

Effect of free glutamine and alanyl-glutamine dipeptide on mucosal proliferation of the human ileum and colon

BACKGROUND/AIMS

Glutamine (Gln) is considered a trophic factor for small intestinal epithelia, which is important during severe illness. Its use in parenteral nutrition is precluded by its instability, a problem that may be overcome by use of the stable dipeptide L-alanyl-L-glutamine (Ala-Gln). The hypothesis was tested that Gln or Ala-Gln may stimulate cell proliferation not only in the ileum but also in the proximal and distal colon and, thus, may contribute to the gut barrier function.

METHODS

Biopsy samples from the normal human ileum, proximal colon, and rectosigmoid were incubated for 4 hours with Gln (2 mmol/L), Ala-Gln (2 mmol/L), and saline (control). Cells in S phase were labeled with bromodeoxyuridine. In longitudinal crypt sections labeled and quiescent cells were counted.

RESULTS

Gln as well as Ala-Gln stimulated crypt cell proliferation in the ileum, proximal colon, and rectosigmoid colon. In ileal specimens, labeling was greater in the entire crypt, whereas in both colonic regions, the trophic effect was confined to the basal crypt compartments.

CONCLUSIONS

Gln and Ala-Gln have trophic effects not only in the ileum, but also in the proximal and distal colon. This could be important during parenteral nutrition when mucosal atrophy may weaken the gut barrier.

Proliferating cell nuclear antigen (PCNA): a new marker to study human colonic cell proliferation

Immunohistochemistry of the S phase related proliferating cell nuclear antigen (PCNA) was studied as an alternative to ex-vivo bromodeoxyuridine (BrdU) immunohistochemistry for assessment of human colonic cell proliferation. From 16 subjects without colonic disease biopsy specimens were collected from five different sites along the colorectum and processed for BrdU and PCNA immunohistochemistry. The mean proliferation index of PCNA was significantly higher at 133% of the value obtained with BrdU. There was, however, a good correlation between the results from both techniques (r = 0.6275; p < 0.05). Decrease in proliferation index along the colorectum was seen with both staining methods but was clearer with PCNA immunohistochemistry (caecum/ascending colon v rectum: 12.0 v 7.2; p < 0.004). The total number of crypt cells also decreased from proximal to distal (134 to 128; p < 0.06) but at no site correlated significantly with the proliferation index. It is concluded that in clinical cell kinetic studies staining for PCNA may serve as an attractive alternative to the BrdU incorporation assay.

Epithelial cell proliferation in the sigmoid colon of patients with adenomatous polyps increases during oral calcium supplementation

To study the effect of oral supplemental calcium on colonic epithelial proliferation, 17 adenomatous polyp patients received 1.5 g Ca2+ as calcium carbonate daily during 12 weeks, while on a calcium constant diet, based on the patients' habitual diet. Seven subsequently continued calcium supplementation for 9 months without dietary restrictions. Epithelial proliferation rate in colonic biopsies, expressed as labelling index (%), was determined with 5-bromodeoxyuridine and immunohistochemistry. Biopsies were taken from the midsigmoid at time of polyp excision and at the end of the intervention period. Median labelling index increased from 6.1% before to 8.7% after 12 weeks calcium (n = 17, P < 0.02). This was due to increased labelling in the basal third of the crypts (11.9 vs 16%), whereas labelling in mid and luminal compartments was not affected. Labelling index remained increased after 1 year calcium supplementation at 8.8%. Crypt length was not affected by calcium. These results are in contrast to those of others, who have shown a decrease of rectal epithelial proliferation during similar doses of calcium. Therefore, the effect of nutritional intervention on colonic epithelial proliferation should be studied in biopsies taken not only from the rectum, but also from more proximal parts of the colon. Caution with respect to large scale intervention studies with calcium in high risk groups is mandatory.

In vitro BrdUrd incorporation of colorectal tumour tissue

This study describes a novel in vitro method for the incorporation of the thymidine analogue, bromodeoxyuridine (BrdUrd), in fresh colorectal tumour tissue. Disaggregation by pronase, collagenase and DNAse resulted in high cell yields of viable single cell suspensions, representative of the original tumour, which could be infiltrated with BrdUrd. A modified ELISA identified optimal incubation times and BrdUrd concentrations. This technique has been used in preliminary studies to investigate two important areas intrinsic in the analysis of BrdUrd colorectal cell proliferation data: 1) to determine the effects of the individual constituents of the cell culture media, in particular glutamine, on BrdUrd incorporation in suspensions of colorectal cells and 2) to examine the denaturation step. This method will have wide applicability in investigations of cell proliferation status in both normal and diseased tissue.

Proliferative activity of urothelial neoplasms: comparison of BrdU incorporation, Ki67 expression, and nucleolar organiser regions

AIMS

To evaluate the proliferative activity of urothelial neoplasms, compare it with that of the normal urinary tract epithelium, and determine its relation to morphological grade and presence of invasion.

METHODS

Multiple biopsy specimens from 53 individuals--eight normal controls, five patients with severe urothelial atypia, and 40 with transitional cell carcinomas (TCCs)--were studied using in vitro bromodeoxyuridine (BrdU) incorporation, Ki67 antigen expression, and quantitation of the nucleolar organiser regions (NORs).

RESULTS

The percentage of nuclei labelled by BrdU (BrdU index) correlated well with the percentage of nuclei expressing the Ki67 antigen (Ki67 index). These proliferation indices were very low (less than 0.1% in 60% of samples) in the urothelium of normal controls and the morphologically unremarkable epithelium of patients with TCCs. Non-invasive TCCs had increased proliferation (BrdU index 6.32 (SD 0.8)%, Ki67 index 5.04 (0.6)% but lagged behind the invasive tumours (BrdU 20.9 (3.2)%, Ki67 18.6 (2.8)%). The average NOR count was 1.57 (0.03) in morphological normal epithelium, which increased progressively with grade in non-invasive TCCs, but varied greatly in invasive tumours and did not correlate with the proliferation indices. The spectrum of values for both proliferation indices and NORs was particularly wide in grade 2 TCCs. Severe atypias without exophytic growth had an increase in BrdU and Ki67 indices comparable with that found in grade 3-4 invasive TCCs; these also had the highest NORs per nucleus.

CONCLUSIONS

The growth potential of urothelial neoplasms is an important indicator of their aggressive course. In particular, growth indices over 10% are strongly associated with the presence of invasion. Papillary grade 2 TCCs show heterogeneity in their growth characteristics which may relate to their diverse clinical course. The mitotic count underestimates the growth potential of papillary TCCs and the addition of proliferation indices such as BrdU incorporation or the Ki67 index may enhance the prognostic accuracy of conventional morphological grading.

The expression of proliferating cell nuclear antigen in paraffin sections of peripheral, node-negative non-small cell lung cancer

Cell proliferation of 40 peripheral, node-negative non-small cell lung cancers (NSCLC) treated with surgery alone was investigated by immunohistochemical analysis with the monoclonal antibody (MoAb) PC10, which recognizes a proliferating cell nuclear antigen (PCNA) in formalin-fixed and paraffin-embedded material. Results were correlated with DNA ploidy and S-phase fraction (SPF) analyzed by DNA flow cytometric study. Mitotic count (MC) was analyzed by light microscopic study and histopathologic features. PCNA immunoreactivity was seen in all samples and confined to the nuclei of cancer, but not to the surrounding, tumor-negative cells; its frequency ranged from 0-70% (median, 15%), and tumors expressed either a low (0-25%, n = 25) or intermediate (26-75%, n = 15) proliferative activity. There was no relationship between PCNA immunoreactivity and tumor stage or among size, histologic type, and mitotic count (MC). Tumors with intratumoral blood vessel invasion (BVI) showed a significantly higher (P less than 0.005) PCNA immunoreactivity than BVI-negative tumors. PCNA scores were significantly higher (P less than 0.005) in DNA aneuploid (n = 22) than in DNA diploid (n = 18) tumors and correlated significantly with the SPF of DNA aneuploid tumors (r = 0.825, P less than 0.0001), but not with diploid tumors (r = 0.002, P = 0.9). Intermediate proliferating tumors had a significantly higher (P less than 0.01) MC than their counterparts. In univariate analysis, significant predictors of survival were tumor classification (T1 versus T2), tumor size (less than or equal to 2.6 cm versus more than 2.6 cm), BVI (BVI-negative versus BVI-positive), MC (less than or equal to 8 versus more than 8), and PCNA immunoreactivity (low versus intermediate). DNA ploidy and SPF did not influence survival significantly. Only PCNA immunoreactivity retained its independent level of significance (P = 0.02) by multivariate analysis. It was concluded that PCNA immunostaining is a simple and clinically useful method for estimating cell proliferation in formalin-fixed, paraffin-embedded tissue of resected peripheral, node-negative NSCLC.

Precursors of colorectal carcinoma. Biopsy and biologic markers

The term biologic marker (biomarker) of colorectal cancer refers in this article to an early preclinical phenotypic characteristic that relates to the risk for developing this cancer. Putative biologic markers in the normal colorectal mucosa of patients at risk include abnormal cell proliferation as determined by kinetic studies, ornithine decarboxylase activity, and polyamine synthesis. Alterations of mucin synthesis have been studied using both histochemical stains and lectin-binding techniques. Blood group and related carbohydrate antigens also have been evaluated as potential biomarkers in the normal mucosa. Biopsy small (less than 5 mm) polyps encountered at endoscopy has become a standard practice. Although a small polyp found to be an adenoma has a low likelihood of harboring high-grade dysplasia or invasive carcinoma, it represents an indicator of risk for colorectal neoplasia. Hyperplastic polyps, however, even though they have certain epidemiologic associations with colorectal neoplasia, are controversial as putative biomarkers of clinical relevance. Current research supports a concept of a field defect of the colorectal mucosa at risk for neoplasia, which may be identified by phenotypic abnormalities of the normal mucosa and the development of small adenomas.

Effect of short-chain fatty acids on the human colonic mucosa in vitro

Fermentable dietary fiber components are known to stimulate colonic crypt proliferation. As these compounds are rapidly degraded to short-chain fatty acids (SCFAs) by the anaerobic microflora, the hypothesis was tested that this trophic effect of fiber may be mediated by SCFAs. Biopsies were taken from normal cecal mucosa of 45 individuals during routine colonoscopy. They were incubated for 3 hours with sodium salts of SCFAs at physiological concentrations (three SCFAs = acetate 60 mmol/L + propionate 25 mmol/L + butyrate 10 mmol/L; acetate 60 mmol/L; propionate 25 mmol/L; butyrate 10 mmol/L) or equimolar NaCl (control). Cell proliferation was measured autoradiographically by subsequent pulse labeling with [3H]thymidine (1 hour). The labeling index (number of labeled cells divided by the total number of cells) was computed for the crypt as a whole and for five equal crypt compartments (compartment 1 = crypt base, compartment 5 = crypt surface). Cecal crypt proliferation was raised significantly in all incubation experiments with SCFAs. Butyrate (10 mmol/L, increase + 89%) and propionate (25 mmol/L, + 70%) were as effective in stimulating proliferation as the combination of three SCFAs (+103%), although the effect of acetate (+31%) was minor. Increasing the butyrate concentration to 25 mmol/L or 60 mmol/L did not result in a further increase of cell labeling. SCFAs stimulated proliferation in the basal three crypt compartments only. An expansion of the proliferative zone to compartments 4 and 5 was not observed. SCFAs, especially butyrate and propionate, are luminal trophic factors for the cecal epithelium.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic phenotypes and colorectal neoplasia

It now appears likely that the development of colonic adenomas and carcinomas involves a series of steps in which environmental or endogenous carcinogens induce or promote neoplasia through the accumulation of multiple, specific genetic mutations. Genetic predisposition to this process may take the form of inherited defects in control of cellular proliferation as in familial polyposis coli, or genetically determined polymorphism which affects enzyme activities relevant to the production or detoxication of carcinogens. Genetic effects may also influence levels of hormones and/or their target cell receptors which regulate the metabolic and proliferative activity of colonocytes. This review highlights data suggesting a role for polymorphism associated with xenobiotic acetylation, hydroxylation, and conjugation with glutathione in the metabolism of potential carcinogens, as well as for dehydroepiandrosterone in the metabolic control of cell proliferation. The study of genetically determined polymorphism in colorectal cancer may provide new insights into the epidemiology of cancer and result in new methods for the detection of higher risk groups.

Calcium and the prevention of colon cancer

Diet is a major determinant of colon cancer risk. Calcium may protect against colon cancer, presumably by binding cytotoxic bile acids and fatty acids. Numerous studies support this proposition. In subjects at risk for colon cancer oral calcium supplementation has been shown to reduce rectal epithelial proliferation rate, thereby supposedly decreasing cancer risk. In contrast to the original hypothesis that phosphate counteracts the effect of calcium, evidence has now been provided that phosphate is crucial for the intraluminal binding of bile acids in complexes of calcium, phosphate, and bile acids. Supplemental calcium has been shown to reduce the cytotoxic potential of fecal water, which is probably attributable to the profound effect of calcium on bile acid and fatty acid metabolism. However, some reservation with regard to the protective ability of calcium seems to be warranted as we found that oral calcium supplementation caused an increase in epithelial proliferation rate in the sigmoid of patients with adenomatous polyps. Further controlled studies evaluating the effects of calcium on the epithelium of different parts of the colon should now be performed.